The present invention relates to an electromagnetic clutch assembly for selectively connecting a source of rotative power with a driven component and, more specifically, to an electromagnetic clutch assembly including an armature disk having a friction material fixedly disposed therein.
It is known in the field of automotive engines to provide an endless belt driven by an output shaft, in which the endless belt is used to transmit the torque of the output shaft to various vehicle components. Specifically, the belt is trained about a plurality of pulley assemblies that are associated with the input shafts of the components to be driven. Certain of such components may also be provided with a clutch sub-assembly that is mounted on the component input shaft to be driven and used to engage and disengage the driven pulley. For example, the input shaft of an air conditioning compressor needs to be driven only when air conditioning within the vehicle is desired. When the air conditioning system is turned on, the clutch sub-assembly engages the pulley to enable the system to be driven. When the air conditioning system is shut down, the clutch sub-assembly disengages the associated pulley, and the pulley will no longer drive the compressor input shaft.
Typically, the clutch sub-assemblies employed for such applications provide resilient structure, such as one or more leaf springs or one or more compression springs, that normally biases the armature disk of the clutch sub-assembly in an axial direction away from the associated component pulley, so that the clutch armature disk remains spaced from the pulley.
When the clutch sub-assembly is activated, a magnetic current in the coils provided as part of the pulley assembly attracts the clutch armature disk. The armature disk then moves against the force of the resilient structure and into engagement with the pulley to enable the pulley to drive the component. Typically, after the armature disk is in engagement with and driven by the pulley, the resilient structure operates in the transmission of torque between the pulley and armature disk.
Conventionally, in instances where additional friction between the pulley member and armature plate has been desired, the pulley member has been provided with a friction material. The friction material is provided in an annular recess machined into the pulley surface facing the armature plate. The friction material is fixedly disposed in the recess so as to provide a friction surface on one side thereof for engaging the armature plate. In the instance that the pulley member is formed with a machined recess therein, the material which transmits the magnetic flux is lessened, thus decreasing the attractive force between the pulley member and the armature plate.
The present invention is based upon the underlying concept of there being significant advantages in providing friction material in a recess stamped in the armature disk. More particularly, it is advantageous to utilize such friction material within the concave configuration or recess of oppositely facing concave and convex surfaces stamped in an annular portion of the armature disk. An advantage of this arrangement is that the stamping operation is more economical to perform than a machining operation. In addition, because no material is removed in stamping a recess, it does not result in a lessening of the material which transmits the magnetic flux, as is the case with a machined recess. Also, because no material is removed during stamping, the rigidity of the disk will not be weakened, as can occur when removing material during machining.
In addition, in some but not all instances, in order to fixedly dispose the friction material within a recess, it may be desirable to use a heat settable adhesive. Because a pulley has typically a much greater thermal mass than the armature plate, it takes a longer time to bring the mass of the pulley up to the necessary processing temperature than what would be required for an armature plate. As a result, processing time and this expense for providing friction material on a pulley is significantly greater than what can be accomplished with an armature plate.
Accordingly, it is an aspect of the present invention to provide an electromagnetic clutch that achieves the advantages noted above.
In accordance with the principles of the present invention, this aspect is achieved by providing an electromagnetic clutch assembly for selectively connecting a source of rotative power with a driven component having an input shaft rotatable about a shaft axis. The electromagnetic clutch assembly features a driven member mounted for rotational movement about the shaft axis. The driven member is rotated about the shaft axis by the source of rotative power. An electromagnetic coil assembly is energizable to generate a field of magnetic flux and a clutch sub-assembly selectively couples the driven member to the shaft responsive to energizing and de-energizing the electromagnetic coil assembly.
The clutch sub-assembly includes an armature disk constructed and arranged to be drivingly connected with the driven component. The driven member and the armature disk have cooperating magnetic flux transmitting portions that enable relative movement between the armature disk and driven member into a cooperating relation. In cooperating relation, the disk and the driven component are engaged via the field of magnetic flux created when the electromagnetic coil assembly is energized and are relatively moved out of the cooperating relation when the electromagnetic coil assembly is de-energized.
The armature disk is stamped within an annular portion thereof to provide oppositely facing convex and concave surfaces in a one-step stamping procedure, and a frictional material is fixedly disposed within the concave configuration of the convex and concave surfaces. The friction material and the driven member have gripping surfaces, which interengage when the magnetic coil assembly is energized.
The invention also contemplates achieving the advantages noted above by an improved method procedural combination.
This aspect is achieved by providing a method of making an armature disk of an electromagnetic clutch assembly. The method comprises forming a disk of magnetic flux transmitting material with an annular portion of the disk stamped to provide oppositely facing convex and concave surfaces. Fixedly disposing friction material within the concave configuration of the convex and concave surfaces within an exposed configuration suitable to interengage with a cooperating clutch member.